Understanding the driving forces behind the nucleation of different polymorphs is of great importance for material sciences and the pharmaceutical industry. This includes understanding the reaction ...coordinate that governs the nucleation process and correctly calculating the relative free energies of different polymorphs. Here, we demonstrate, for the prototypical case of urea nucleation from the melt, how one can learn such a one-dimensional reaction coordinate as a function of prespecified order parameters and use it to perform efficient biased all-atom molecular dynamics simulations. The reaction coordinate is learnt as a function of the generic thermodynamic and structural order parameters using the “spectral gap optimization of order parameters (SGOOP)” approach Tiwary, P. and Berne, B. J. Proc. Natl. Acad. Sci. U.S.A. (2016) and is biased using well-tempered metadynamics simulations. The reaction coordinate gives insights into the role played by different structural and thermodynamics order parameters, and the biased simulations obtain accurate relative free energies for different polymorphs. This includes an accurate prediction of the approximate pressure at which urea undergoes a phase transition and one of the metastable polymorphs becomes the most stable conformation. We believe the ideas demonstrated in this work will facilitate efficient sampling of nucleation in complex, generic systems.
Rate-distortion optimization (RDO) is widely used in video coding, which plays a critical role in enhancing the coding efficiency substantially. Currently, the RDO process is performed in a way that ...coding efficiency of each coding unit (CU) is maximized independently without considering the dependency among CUs. As we know, in the current hybrid video coding structure, spatial/temporal prediction techniques are extensively used, which introduce strong dependency among CUs. In this paper, we investigate RDO with inter-frame dependency, where the impact of coding performance of the current CU on that of the following frames is considered. Accordingly, an RDO scheme taking the inter-frame dependency into account is proposed by adapting the Lagrangian multiplier. The experimental results show that the proposed scheme can achieve about 3.22% and 3.19% BD-rate saving in average over the state-of-the-art High Efficiency Video Coding (HEVC) reference software HM15.0 in the low-delay P (LDP) and low-delay B (LDB) coding structures, respectively, with no extra encoding time. The proposed scheme can obtain a significantly higher coding gain than the multiple quantization parameter (MQP) (±3) optimization technique that would greatly increase the encoding time by a factor of about six. Coupled with MQP optimization, the proposed scheme can further achieve about 5.96% and 5.57% BD-rate savings in average over the HEVC and about 4.03% and 4.07% over the HEVC with MQP optimization, under the specified common test conditions for LDP and LDB coding structures, respectively.
A copper-catalyzed decarboxylative cascade cyclization of propargylic cyclic carbonates/carbamates with pyridinium 1,4-zwitterionic thiolates is developed. A range of fused polyheterocyclic compounds ...are obtained in moderate to good yields with excellent diastereoselectivities. Of particular note is that four new bonds (two C–C, one C–O/N, one C–S) and four new stereocenters could be efficiently embedded into the tetracyclic fused scaffolds in a single step.
Exosomes are a subset of extracellular vesicles that carry specific combinations of proteins, nucleic acids, metabolites, and lipids. Mounting evidence suggests that exosomes participate in ...intercellular communication and act as important molecular vehicles in the regulation of numerous physiological and pathological processes, including cancer development. Exosomes are released by various cell types under both normal and pathological conditions, and they can be found in multiple bodily fluids. Moreover, exosomes carrying a wide variety of important macromolecules provide a window into altered cellular or tissue states. Their presence in biological fluids renders them an attractive, minimally invasive approach for liquid biopsies with potential biomarkers for cancer diagnosis, prediction, and surveillance. Due to their biocompatibility and low immunogenicity and cytotoxicity, exosomes have potential clinical applications in the development of innovative therapeutic approaches. Here, we summarize recent advances in various technologies for exosome isolation for cancer research. We outline the functions of exosomes in regulating tumor metastasis, drug resistance, and immune modulation in the context of cancer development. Finally, we discuss prospects and challenges for the clinical development of exosome-based liquid biopsies and therapeutics.
The residue of Chinese Herbs has been increasing at a rapid rate with the development of Traditional Chinese Medicine. As the residue become solid waste, serious second pollution can result to waters ...and soil. In the meanwhile, substance abuse had led to an antibiotic's accumulation in aquatic ecological environment. In this study, a residue from a Chinese herbal medicine, Flueggea suffruticosa, was used to prepare biochar for antibiotics pollution control. The biochar was modified by zinc chloride (Zn-BC) and used as an adsorbent to remove tetracyclines (TCs) from water. The surface area of Zn-BC was 1556 m2/g, and tetracycline (TC), chlortetracycline (CTC), and oxytetracycline (OTC) were chosen as target pollutants to detect the adsorptive capacity of Zn-BC. The adsorption process can be described by the pseudo-second-order model and Langmuir model, and the influences of pH and ionic strength on adsorption were also investigated. According to the Langmuir model, the maximum adsorption capacity of Zn-BC to CTC, TC and OTC was 200.0, 188.7 and 129.9 mg/g. Hydrogen bonding and electrostatic interaction played dominant roles in the adsorption process and the adsorption process was spontaneous. The biochar derived from the Chinese herbal medicine residue is an effective adsorbent for removing TCs from wastewater.
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•A Chinese herbal medicine residue, Flueggea suffruticosa, was used to make biochar.•The biochar was modified by zinc chloride and the surface area was 1556 m2/g.•The Zn-BC was used to adsorb tetracycline, chlortetracycline, and oxytetracycline.•The maximum adsorption capacity to TC, CTC and OTC was 188.7, 200.0 and 129.9 mg/g.•Hydrogen bonding and electrostatic interaction play dominant roles in the adsorption.
Based on an equivparticle model, we investigate the in-medium quark condensate in neutron stars. Carrying out a Taylor expansion of the nuclear binding energy to the order of ρ3, we obtain a series ...of EOSs for neutron star matter, which are confronted with the latest nuclear and astrophysical constraints. The in-medium quark condensate is then extracted from the constrained properties of neutron star matter, which decreases non-linearly with density. However, the chiral symmetry is only partially restored with non-vanishing quark condensates, which may vanish at a density that is out of reach for neutron stars.
Drop impact causes severe surface erosion, dictating many important natural, environmental and engineering processes and calling for substantial prevention and preservation efforts. Nevertheless, ...despite extensive studies on the kinematic features of impacting drops over the last two decades, the dynamic process that leads to the drop-impact erosion is still far from clear. Here, we develop a method of high-speed stress microscopy, which measures the key dynamic properties of drop impact responsible for erosion, i.e., the shear stress and pressure distributions of impacting drops, with unprecedented spatiotemporal resolutions. Our experiments reveal the fast propagation of self-similar noncentral stress maxima underneath impacting drops and quantify the shear force on impacted substrates. Moreover, we examine the deformation of elastic substrates under impact and uncover impact-induced surface shock waves. Our study opens the door for quantitative measurements of the impact stress of liquid drops and sheds light on the origin of low-speed drop-impact erosion.
The aim of this study was to compare the accuracy of implant placement by using the conventional freehand method, the surgical guide alone, the dental navigation system alone, and the dental ...navigation system with a surgical guide. The participants were aged 20 years or older and were requiring dental implant surgery according to an assessment made by a dentist between July 2014 and December 2017. A total of 128 dental implants were inserted, 32 dental implants in each group, and participants with similar or identical age (i.e., 20-50 years or 50 years or above) and missing tooth locations were paired for comparison. Accuracy was measured by overlaying the real position in the postoperative Cone Beam Computerized Tomography (CBCT) on the virtual presurgical placement of the implant in a CBCT image. Using the dental navigation system with a surgical guide could help dentists to position implants more accurately. Total, longitudinal, and angular error deviation were significantly different (
< 0.0001). The same level of accuracy could be obtained for the different jaws and tooth positions. The one-way analysis of variance (ANOVA) showed that the total, longitudinal, and angular errors differed significantly (
< 0.0001). A comparison of the four dental implant surgical methods indicated that the combination of a dental implant navigation system and a surgical guide kit achieved the highest accuracy in terms of the different tooth positions and jaws.
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